[PATCH v2 05/36] x86/entry/64/compat: Fix SYSENTER's NT flag before user memory access

From: Andy Lutomirski
Date: Mon Oct 05 2015 - 20:57:55 EST


Clearing NT is part of the prologue, whereas loading up arg6 makes
more sense to think about as part of syscall processing. Reorder
them.

Signed-off-by: Andy Lutomirski <luto@xxxxxxxxxx>
---
arch/x86/entry/entry_64_compat.S | 18 +++++++++---------
1 file changed, 9 insertions(+), 9 deletions(-)

diff --git a/arch/x86/entry/entry_64_compat.S b/arch/x86/entry/entry_64_compat.S
index a9360d40fb7f..aa76864a8a6b 100644
--- a/arch/x86/entry/entry_64_compat.S
+++ b/arch/x86/entry/entry_64_compat.S
@@ -89,15 +89,6 @@ ENTRY(entry_SYSENTER_compat)
sub $(10*8), %rsp /* pt_regs->r8-11, bp, bx, r12-15 not saved */

/*
- * no need to do an access_ok check here because rbp has been
- * 32-bit zero extended
- */
- ASM_STAC
-1: movl (%rbp), %ebp
- _ASM_EXTABLE(1b, ia32_badarg)
- ASM_CLAC
-
- /*
* Sysenter doesn't filter flags, so we need to clear NT
* ourselves. To save a few cycles, we can check whether
* NT was set instead of doing an unconditional popfq.
@@ -106,6 +97,15 @@ ENTRY(entry_SYSENTER_compat)
jnz sysenter_fix_flags
sysenter_flags_fixed:

+ /*
+ * no need to do an access_ok check here because rbp has been
+ * 32-bit zero extended
+ */
+ ASM_STAC
+1: movl (%rbp), %ebp
+ _ASM_EXTABLE(1b, ia32_badarg)
+ ASM_CLAC
+
orl $TS_COMPAT, ASM_THREAD_INFO(TI_status, %rsp, SIZEOF_PTREGS)
testl $_TIF_WORK_SYSCALL_ENTRY, ASM_THREAD_INFO(TI_flags, %rsp, SIZEOF_PTREGS)
jnz sysenter_tracesys
--
2.4.3

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